The pads had settled to varying degrees with 8 of the 10 having settled 1 (±0.5) inch and requiring only stabilization and the two remaining, with settlement in excess of 3.5 inches, requiring lift and stabilization.

QUICK FACTS:

Location: South Dakota Wind Energy Farm

Problem: Settled Transformer Pads at Base of Turbines

Project Considerations: Transformers + Pads, Weight = 29,000 lbs. ea.

All the transformers were mounted on individual 15 ft. x 8.5 ft. x 8 in. thick precast pads which were partially supported on precast cabling vaults and lean concrete structural support on the unloaded side of the pad and compacted earth on the loaded side. The settlement to the loaded side of the transformers caused the pad to tip on the inside edge of the concrete vault.

Settlement had occurred within one and a half years of installation and was determined to be due to combination of factors including insufficient compaction surrounding the transformer pad location and freeze thaw cycles.

Voids were present in varying degrees under all of the slabs.

Concerns about how to return the two worst transformers to level, coupled with questions about material containment in the target area and mechanical stresses on the precast transformer pad were addressed and described under Proposed Solution.

PROPOSED SOLUTION: 

URETEK ICR proposed two solutions. The first addressed stabilization of soils below each of the transformer pads. The second ensured a sure, steady, and complete lift of the two worst pads to level, coupled with void fill and soil stabilization.

The eight pads which had settled <1.5 inches were slated to have URETEK DEEP INJECTION® work performed with the goal of stabilization of sub soils to prevent future settlement. Although lifting back as close to original grade was a goal, it was not specified as the ability of the soils to keep the material contained could not be determined prior to application.

• A single depth injection was performed at 4 locations parallel to and approximately one foot from the settled edge of the pad.

• A secondary injection was performed by angling the URETEK DEEP INJECTION® probes at an approximate 45˚ angle, placing the injection point under the transformer pad.

It was determined prior to submission of the proposed solution that the precast transformer pads were capable of bearing the weight of the transformer while under lifting stresses from the outside unsupported edge of the pad. Therefore mechanical lifting options were incorporated, in the two worst cases, to provide a an assisted lift assuring that material containment issues were alleviated.

• Four 20 ton mechanical lifting devices were dug in and spaced along the settled side of the pad with load distribution taken into consideration.

• Lifting surfaces were covered with wood to prevent direct contact with the pads.

• The mechanical lifting system easily lifting the slab to within 1 inch of desired grade.

• Pads were chocked and the lifting devices un-weighted to ensure the slab would remain at desired grade during void filling operations. Upon verification of stability, closed cell expanding polymer material was injected into the void space below the pad and allowed to set.

• Finally, all chocks were removed and URETEK DEEP INJECTION® process was used as described above.

Three days were allotted for project completion.

DOING THE PROJECT: 

PROJECT SUMMARY:

URETEK ICR counts this as a successful project. This is due to these factors:

1. The project was completed within the tight timeline and budget – with no surprises! (This project required 3 days)

2. The use of the URETEK Deep Injection® process was able to successfully lift and stabilize all 10 transformer pads, exceeding the original customer requirement

3. The customer now knows of a fast and cost effective solution to settled transformer pads.

BENEFITS:

URETEK ICR’s repair strategy cost substantially less and took substantially less time than other considered repair methods. Our crews were able to the project in low (10 degrees) temperatures, when the customer needed it done, thereby maximizing the productivity of the wind farm and reduce any future transformer maintenance or repair costs. And, because our materials are environmentally friendly (NSF 61 Certified) the repair will not contribute to any future ground or water contamination issues.

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- Team URETEK

Foundation problems due to drought conditions can be minimized through proper moisture levels in the soil.  Maintaining constant moisture content under slabs is a real challenge given the extremes of our Texas weather.  Most of our Texas soils are highly expansive, meaning that as they absorb water, they swell, and as they lose water, they shrink. Soils tend to dry out (and shrink) during the summer and to absorb water (and swell) during the winter and spring.  As the soil under a house shrinks and swells with the seasons, the house and foundation will move up and down. As long as the foundation movement is not enough to cause significant cosmetic damage, or even minor structural damage, it should not be considered a problem. In fact, some seasonal minor drywall cracks or sticking doors can almost be expected in our area.

The key to proper foundation maintenance is to be diligent in your irrigation program, but at the same time, to be sure your drainage is adequate. (Poor drainage can cause a completely different set of problems.)

IRRIGATION

Effective irrigation is best accomplished with an underground foundation watering system; automated systems that monitor soil moisture and irrigate as needed are available from several different local contactors. Soaker hoses will provide you with many of the same benefits, if utilized properly. The best way to use a soaker hose is to bury it about three inches deep, one foot from the edge of your foundation. Placing the hose a short distance from the foundation allows the water to soak into the soil evenly. An automated underground sprinkler system can be just as effective.  Be sure that it waters the soil next to the foundation, and check it periodically to be sure it is working properly.  And don’t neglect to water during the winter months as well, when we sometimes experience extended periods without rain.

Obviously, it is necessary to water more during hot, dry weather and less during cold, damp weather. The amount of water required to keep a foundation stable during the summer can be surprisingly large. A single large tree can remove as much as 150 gallons of water, or almost 20 cubic feet of water, from the soil each day. Shrubs and other plants can also remove large quantities of water. During persistent hot, dry weather, it may be necessary to water a foundation daily. Watering should supply enough water to keep the moisture content in the soil under the foundation constant. If the amount of water applied is only enough to keep the surface damp, the watering program will not work. Obviously, the homeowner is the only one who can weight the benefits of controlling foundation movement versus the increased size of the water bill.

During periods of drought, it is suggested to utilize your soaker hoses on an every-other-day basis, for an hour or so each time.

DRAINAGE

Water pooling against or near your foundation can result in “heaving” (where the swelled soil actually lifts the foundation above its intended elevation), or it can cause the soil under the foundation to lose its load bearing capacity, resulting in settlement.  To guard against these problems, the general grade of your yard should slope gently away from the home, and roof drainage downspouts should be extended several feet away from the foundation.  If the general slope of your yard cannot be easily changed, then some form of surface or below grade drainage system may be needed.  Consult with a qualified foundation repair or landscape contractor to find out what will work best for your particular situation.

URETEK ICR representative Scott Turnage traveled to the resort in order to assess the evidence of settlement, review the forensic geotechnical report, and determine the approximate size of the voids under the deck. This examination revealed that an approximately 1,200 square foot portion of the deck had settled up to 1.0”, resulting in concrete cracks and gaps below the walls, with voids of up to 24.0” under certain portions of the stamped, concrete surface. The spa structure itself has also settled, evidenced by cracking in the sidewalls, below the coping.

URETEK ICR proposed a comprehensive solution using The URETEK Method® to void fill under the deck and lift it back to its proper position, and utilization of the URETEK Deep Injection® Process to inject at depth under the spa for void filling and stabilization.

Upon acceptance of the proposal by the general contractor (and a change order to do additional areas), URETEK mobilized at the job site. Void filling beneath the deck was accomplished first, along with lifting of the deck where needed.

URETEK then turned their attention to solving the deeper problems, with utilization of the patented URETEK Deep Injection® Process. Soil borings indicated voids were present at depth of nearly 11.0’, surrounded by soft soils, so technicians drilled to that level, then inserted copper tubing to the same depth. As URETEK 486 material was injected, it rapidly expanded filling voids and, always following the “path of least resistance,” fractured and squeezed the loose soils. This process was continued until resistance of the soil was detected at the surface, by a “bump” on the laser detector, insuring that the soils were sufficiently densified to support the load of the water filled spa.

The entire job was completed within two days, while resort guests enjoyed the pool a mere 25 feet away. Resort management was pleased that the process meant no disruption in services for their guests, and the general contractor was pleased at the short timeframe for the project and the cost (less than 20% of the cost of replacement of the structure).

The Heifer International building was commissioned in 2002 and completed in February 2006. It was the first Platinum LEED (Leadership in Energy and Environmental Design) certified building in Arkansas and the only one is the South-Central US. There are less than 50 LEED certified buildings in the entire country. The building site started with an old rail yard site known as “Brown-field” and construction 75,000 tons of earth from the area and creating wetlands to store, control and reuse the surface groundwater. Abandoned buildings on the property were crushed and reused in the concrete and mortar portions of the building and steel and wood were recycled too. Bamboo was used for flooring since it grows quickly and there is water is a water collection tower integrated into the building that captures runoff from the roof. This water is used in place of municipal water resources to run the building. The building is only 62’ wide at its greatest width which allows all workspaces to benefit from the natural light provided by the sun. The design is optimized to provide heat in the winter and cooling in the summer and for those of you that would like to consider working at Heifer International…wear comfortable shoes because the elevators are very slow, encouraging employees to take the stairs.

The overall master plan for the new Heifer International Center is a series of concentric rings that expand outward form a central gathering space. The deign is not only practical; it’s also symbolic, representing the “ripple effect” created from Heifer’s unique Passing on the Gift cornerstone. Included in these concentric rings are 8’ wider sidewalk panels that follow the natural curve of the building, and this is where URETEK’s “Simple Solution for Complex Problems” comes in. The sidewalk panels had begun to experience settlement of up to 2” in various areas, creating trip hazards and concerns about the replacement costs for over 1,300 square feet for recycled concrete. While replacing the panels was an option, it wasn’t necessarily the best solution… monetarily or ecologically.

The sidewalk panels were constructed with crushed concrete from the abandoned buildings on the property so replacing them was not the “Greenest” solution available, and the cost to replace approximately 1,300 square feet of recycled concrete was approximately 5-6 times more than URETEK’s solution of supporting and re-aligning the panels. Time was also a factor since construction was scheduled to start of the next phase of the Center and the panels needed to be repaired before the next phase of construction began. After reviewing the proposed repair plan, Heifer International chose to proceed with “The URETEK Method.”

URETEK began work at 7:30am and by 5:00pm had supported and realigned ten large concrete panels. The process began with URETEK’s trained technicians drilling a series of dime sized holes through the panels at approximately 4-8’ apart. The dime size holes were then used to inject our patented hydro-insensitive expanding polymers foam beneath the panels where it expanded to stabilize the soils and lift the panels within 1/10” accuracy. During the injection process, URETEK’s patented material reached full expansion within 15 seconds and was traffic ready within 15 minutes. URETEK’s material did not contribute to future settlement problems because it weighs much less than some of the alternative solutions to concrete lifting using injection technology. And finally, URETEK’s environmentally neutral material provided an eco-friendly solution to an eco-friendly building!

In summary, URETEK was able to fulfill all of Heifer’s needs. The project was completed quickly with environmentally neutral materials and at a price that was much less than the cost to rip and replace. So remember, if you have concrete settlement issues, whether it is at home or building foundation, drive lanes, parking lots, or even the sidewalks for a Platinum LEED certified building, URETEK offers a “Simple Solution to Complex Problems.”

If a structural or geotechnical challenge seems insurmountable, URETEK would like to take a look at it.  If there are no other alternatives, URETEK wants to see how it can help.  Occasionally, a project comes along that requires ultimate attention to detail and the combination of many solutions that come not only from URETEK processes, but its people as well.  Such as the case for Ameristar, currently the largest ornamental fencing company in the world. Located in Oklahoma, this facility boasts of a high-volume, state-of-the-art rollforming, metal processing, powder coating equipment. The equipment used to move the steel coils of fencing across the manufacturing line require precise balance and an extremely strong concrete foundation to supply the turnstile with the proper footing to complete such a heavy task.  A small shift or tilt from a turnstile could be disastrous for the company. URETEK ICR Oklahoma received a call from one of the company’s engineers stating that one of the turnstiles was “listing” to the south when rotated looking like the “Leaning Tower of Pisa.”  Each turnstile has four arms to hold each coil, when three coils are unloaded the remaining coil’s weight caused the turnstile to shift (about -1/2”) due to unstable soil at the base of the turnstile.

Each steel coil weighs 50,000lbs. along with the concrete foundation measured at 30 inches thick under the turnstile puts a live load on the soil to be around 250,000lbs. Due to the heavy nature of the project, URETEK ICR Oklahoma consulted with various engineers and specialist of URETEK USA (Roads & Highways) along with URETEK ICR (Industrial, Commercial) divisions to form a solution. URETEK Roads & Highways division, has over a decade of experience using expanding polymers to lift extremely heavy loads (Related article: “Leaning Tower of Milk”). URETEK USA also specializes in airport runway stabilization where 30+ inches of concrete is common.

After a thorough evaluation a specialized repair plan was developed using both The URETEK Method® (injection of high density structural grade polymer directly below the base or footing of the settled concrete to lift or stabilize concrete) and URETEK’s Deep Injection® Process (injection of high density expanding polymers at depth to solidify and compact the soil to increase the load bearing capacity under heavy structures).

As part of the execution phase of the repair, ICR Oklahoma diagramed the base of the turnstile in a clock face manner. This layout allowed the operations to accurately lift the most distressed portion of the foundation first. While drilling 1/2” injection holes under the turnstile, the crew confirmed the foundation to be approximately 30” thick. URETEK’s Deep Injection® Process was used while the turnstile was in the “dead load” or unloaded condition. The Deep Injection process raised the turnstile +.6 inches. The turnstile was then put in the “live load” or loaded condition with a 50,000 pound coil of steel on each arm bringing the total weight to approximately 250,000 lbs. URETEK’s Deep Injection Process was used again in the planned manner resulting in another +.6 inches of lift. After a set of injections was made, operations then used The URETEK Method™ in a grid pattern on 4 foot centers surrounding the base of the Turnstile to stabilize and fill any remaining voids. The turnstile was then rotated several times with one arm loaded trying to simulate the original failure. The turnstile remained stable and level during all rotations. The total amount of lift was recorded at +1.2 inches.

Completed in 6 hours (after hours) the restoration of the turnstile resulted in no down time for Ameristar’s production line.

Needing to accurately identify the location of the voids and weak soils, URETEK utilized a ground penetrating radar system. As a quality control measure, URETEK also used a dynamic cone penetrometer to confirm the findings and establish the depth of the problem. A visual can be seen (see picture to the right) of actual soil seepage into one of the 12’ diameter pipes that caused the sinkholes. The assessment of the situation indicated 17,000 square feet of the parking lot required stabilization and/or sealing of underground joints.

After gathering all possible data collected by URETEK and the GPR contractor, a solution was designed and approved by the customer. URETEK first sealed 26 separated joints identified in the detention basin system. Many joints required sealing the entire circumference of the joint. URETEK used small, 5/8 inch injection holes drilled from the inside of the pipe to the soil surrounding pipe to deploy the patented, moisture resistive , structural grade polymer. The polymer, which has an expansion ratio of 20:1.0, effectively sealed the pipe while also stabilizing the eroding soil around the pipe (see below). Secondly, URETEK stabilized the base soils beneath the parking lot using a grid pattern for injection. The injection probes used were placed 3.5’ into the soil to inject the weak strata shown by the GPR unit. This effectively increased the load bearing capacity of the soil to support customer traffic and delivery trucks. The total project was completed in six days with three of those days dedicated to surface work. Downtime was kept to a minimum and the customer was very pleased with the results which included a fully functional underground drainage system. URETEK was ultimately chosen as the ideal solution due to the minimal disruption to customer traffic, the speed at which the solution could be implemented, and the cost effectiveness of the overall solution.